The invention relates to storing a frame header, for example in connection with a network controller.
Referring to FIG. 1, a server 12 may communicate with a client 10 by transmitting packets 8 of information over a network 18 pursuant to a network protocol. As an example, the network protocol may be a Transmission Control Protocol/Internet Protocol (TCP/IP), and as a result, the client 10 and server 12 may implement protocol stacks, such as TCP/IP stacks 17 and 19, respectively. For the client 10 (as an example), the TCP/IP stack 17 conceptually divides the client""s software and hardware protocol functions into five hierarchical layers 16 (listed in hierarchical order): an application layer 16a (the highest layer), a transport layer 16b, a network layer 16c, a data link layer 16d and a physical layer 16e (the lowest layer).
More particularly, the physical layer 16e typically includes hardware (a network controller, for example) that establishes physical communication with the network 18 by generating and receiving signals (on a network wire 9) that indicate bits of the packets 8. The physical layer 16e recognizes bits and does not recognize packets, as the data link layer 16d performs this function. In this manner, the data link layer 16d typically is both a software and hardware layer that may, for transmission purposes, cause the client 10 to package the data to be transmitted into the packets 8. For purposes of receiving packets 8, the data link layer 16d may, as another example, cause the client 10 to determine the integrity of the incoming packets 8 by determining if the incoming packets 8 generally conform to predefined formats and if the data of the packets comply with checksums (or cyclic redundancy check (CRC))of the packets, for example.
The network layer 16c typically is a software layer that is responsible for routing the packets 8 over the network 18. In this manner, the network layer 16c typically causes the client 10 to assign and decode Internet Protocol (IP) addresses that identify entities that are coupled to the network 18, such as the client 10 and the server 12. The transport layer 16b typically is a software layer that is responsible for such things as reliable data transfer between two end points and may use sequencing, error control and general flow control of the packets 8 to achieve reliable data transfer. The transport layer 16b may cause the client 10 to implement the specific network protocol, such as the TCP/IP protocol or a User Datagram Protocol (UDP) or Realtime Transport Protocol(RTP) which exists on top of UDP, as examples. The application layer 16a typically includes network applications that, upon execution, cause the client 10 to generate and receive the data of the packets 8.
Referring to FIG. 2, a typical packet 8 may include an IP header 20 that indicates such information as the source and destination IP addresses for the packet 8. The packet 8 may also include a security header 23 that indicates a security protocol (e.g. IPSec) and attributes of the packet 8 and a protocol header 22 (a TCP or an UDP protocol header, as examples) that is specific to the transport protocol being used. As an example, a TCP protocol header might indicate a TCP destination port and a TCP source port that uniquely identify the applications that cause the client 10 and server 12 to transmit and receive the packets 8. The packet 8 may also include a data portion 24, the contents of which are furnished by the source application. The packet 8 may include additional information, such as a trailer 26, for example, that is used in connection with encryption and/or authentication of the data portion 24.
Referring to FIG. 3, as an example, a TCP protocol header 22a may include a field 30 that indicates the TCP source port address and a field 32 that indicates the TCP destination port address. Another field 34 of the TCP protocol header 22a may indicate a sequence number that is used to concatenate received packets of an associated flow. In this manner, packets 8 that have the same IP addresses, transport layer port addresses (and security attributes), are typically part of the same flow, and the sequence number indicates the order of a particular packet 8 in that flow. Thus, as an example, a packet 8 with a sequence number of xe2x80x9c244xe2x80x9d typically is transmitted before a packet 8 with a sequence number of xe2x80x9c245.xe2x80x9d
The TCP protocol header 22a may include a field 38 that indicates a length of the header 22a, a field 44 that indicates a checksum for the bytes in the header 22a and a field 40 that indicates control and status flags.
In order to transmit data from one application to another over the network wire, the data is segmented into frames. The maximum number of bytes that can be packed into one frame is called the maximal transmit unit (MTU). Thus, the operating system may pass data units down to hardware, such as network controller, in units that correspond to the MTU.
There is overhead associated with segmenting the data into MTUs, creating the frame header at all layers, and transmitting multiple messages down the stack to a miniport driver or other drivers for other operating systems or hardware. A driver, containing device specific information, communicates with non-device specific port drivers that in turn communicate with the protocol stack on behalf of the system. When the operating system wishes to offload some of that overhead, it may pass data to the miniport driver or hardware in data units larger than the MTU. This type of transfer is generally called a large send. The miniport driver or hardware can now segment the data and create the framing information.
Generally a large send requires that header information be recreated for successive frames. However, this will result in delay and overhead and also requires the header to be read across the system bus with every segment prior to its modification. This may increase the overall delay to complete the data exchange between the client and the server and consume bus resources that are important especially for server and multiple controller systems.
Thus, there is a continuing need for implementing a large send in a way which reduces the consumption of bus resources.
In one embodiment of the invention, a method for use with a computer system, includes receiving output data from the computer system, extracting the header of the packet; storing a header from said data in a header memory, retrieving the header from header memory and parsing the header to add additional information to the header.